October 24, 2022

Start Your Engines! Enhancing Upstream Capacity with 204Mhz Digital Return

In this blog, we discuss how Precision OT, with its unique network engineering experience and suite of digital return transceivers that includes both DWDM fixed and tunable optics, can help cable operators turn their high-split digital return goals into reality.

The Challenge

HFC network operators are increasingly looking for high-split digital return solutions to meet growing demand for speeds of up to 1 Gbps (and, in the not-too-distant future, 6 Gpbs) in the upstream part of their networks. However, pursuing 204MHz high-split upgrades within the HFC network is not an easy task. From questions around interference to a need for more space, power, cable modem termination ports, upgraded amplifiers and cost-effective, reliable transceivers, the journey is complex and requires considerable planning and testing. Yet, it’s something that cable operators like Cox, Charter, Shaw and others are moving forward with.

What’s New with High-Split Digital Return Technology?

Digital return technology (DRT) is fundamentally a question of shifting from analog to digital. At a high-level, DRT operates by converting customers’ RF analog signals into optical return transmission back to the headend. An analog to digital converter (ADC) accomplishes the initial digitization while the conversion to an optical signal is completed in the outdoor fiber node. Once at the headend, the optical transmission is turned back into an RF analog signal using a digital to analog converter (DAC). Essentially, DRT creates a digital path from the node to the headend using already-existing infrastructure. This means network operators do not necessarily have to spend more money on laying new fibers within their HFC networks.

As the industry explores providing higher upstream bandwidth services within HFC networks, new DOCSIS standards are also prompting cable operators to consider undertaking their own high-split upgrades in preparation for the future. Here is a table demonstrating the vast improvement in upstream capabilities that current and newer DOCSIS standards facilitate.

Table 1. Comparison of DOCSIS standards

DOCSIS Standard

DOCSIS 3.0

DOCSIS 3.1

DOCSIS 4.0

Downstream Capacity

1 Gbps

10 Gbps

10 Gbps

Upstream Capacity

200 Mbps

1-2 Gbps

6 Gbps

Split MHz

42, 65, 85

42, 65, 85, 204

300, 396, 492, 684

Compared to DOCSIS 3.0, DOCSIS 3.1 supports the use of 204 MHz high splits to enable peak rates of up to 1 Gpbs in the upstream. Going up to 6 Gpbs in the upstream will require adopting DOCSIS 4.0 ultra-high splits from 300 MHz to 684 MHz. However, DOCSIS 4.0 will likely not be implemented for consumers until 2024 or 2025. Currently, the focus for cable operators is on upgrading their networks to enable DOCSIS 3.1.

Even though cable operators can use existing plant architecture to upgrade from DOCSIS 3.0 to 3.1, implementing a 204 MHz high-split architecture still brings an entire set of technical, logistical, and operational considerations. Cable operators need to consider the readiness of their wide area networks, distribution hubs, inside/outside plant, support systems, and customer premise equipment (CPE) devices. When it comes to designing and preparing remote nodes for a high-split upgrade, an operator’s choice of optical transceivers for the return path becomes a specific, yet highly impactful decision.

How Precision OT Can Help HFC Network Operators with 204MHz Digital Return

When it comes to digital return transceivers for high-split remote node upgrades, cable operators have a few technological and economic aspects to consider. It’s not just about whether the optics are DWDM-capable, whether they come in an SFP or SFP+ form factor or whether they cover 80km or 100km link distances. It’s also about whether they have the following capabilities:

  1. Resilient for seamless operations in fluctuating temperatures or harsh environments
  2. Able to plug and play within existing network infrastructure
  3. Able to support a network operator’s longer-term upgrade roadmap
  4. Affordable to purchase, inventory and maintain on a long-term basis

At Precision OT, we’ve worked with many customers to provide them with the optical transceivers for their digital return requirements. Many, however, are beginning to seek optics that can help minimize their operating expenditures while still performing reliably. In other words, cable operators are once again asking the question of “how can we do more with greater efficiency?” For a growing number of customers, the answer lies in tunable optics.

As we’ve written in an earlier blog, tunable optics help cable network operators cut down both on the amount of inventory they need to stock and the time and labor it takes to replace the optics when wavelength adjustments are needed. While individual tunable transceivers can cost more to purchase than fixed-wavelength optics, they minimize cost and maximize flexibility when considered in the context of the system overall. When undertaking high-split upgrades for 204 MHz digital return, the question of whether tunable optics are the right option is really a question of balancing expected CAPEX with projected, long-term OPEX. And this kind of question is exactly where Precision OT can help.

As a team of network experts that performs rigorous testing in our onsite labs, we offer a range of fixed-wavelength and tunable optics for high-split digital return requirements. All the models we offer are also I-Temp certified, which means they can perform reliably in remote nodes wherever they are located. Wherever you are in your journey to 204 MHz digital return, we can support you with expert advice, reliable solutions and ingenious customization capabilities such as multi-platform optics to fit each customer’s network vendor diversity. Ask your questions today.

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